Cancer progression is determined by intrinsic changes in the developing cancer cells as well as by important interactions between the cancer cells and other components of the tumor microenvironment. Lung cancer is the leading cause of cancer death in the United States and woridwide. Despite recent progress in lung cancer treatment, long-term survival rates for individuals with late-stage disease remain very poor. Using a wellstudied mouse model of invasive and metastatic non-small cell lung cancer (NSCLC) as well as human lung cancer cell lines and human cancer specimens, we will characterize and functionally test components of the extracellular matrix (ECM) and a specific cell type within tumor stroma for their effects on tumor biology, including tumor progression. Project 2 has three Specific Aims. Aim 1 is focused on functional characterization of Tenascin C (TNC), an ECM component that has been implicated in tumor progression in a variety of settings, including in this model of NSCCL. We will use both cell-based and whole animal approaches to examine the effects of manipulation of TNC function on cancer progression. In Aim 2, we will use an ECM microarray to identify additional ECM components that participate in cancer cell adhesion and may affect aspects of invasive and metastatic behavior. Screening studies, which will be carried out with cells of both mouse and human origin, will be followed by functional analysis. Aim 3 utilizes advanced methods in genetic engineering to manipulate cancer-associated fibroblasts within established, late-stage NSCLC, in order to investigate the consequences of gross and more subtle alternations within this cell population for cancer cell biology. The methods developed for this purpose can also be applied to the study of other cancer-associated cell populations within the tumor microenvironment. This project has the potential to uncover tumor-stromal interactions that mediate critical aspects of cancer progression. The functional validation of these interactions could lead to new therapeutic strategies for treating NSCLC in humans and/or to prevent its progression. Project 2 is well integrated into the larger structure of this TMEN application through multiple interactions with each of the other projects and investigator groups.